Re: git: a1d71cebc05c - main - fstatat(2): restore AT_EMPTY_PATH handling

On 5/2/23, Mateusz Guzik <mjguzik@gmail.com> wrote:
> right, this should do it
>
> diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
> index e4977392349f..b583eed5e249 100644
> --- a/sys/kern/vfs_cache.c
> +++ b/sys/kern/vfs_cache.c
> @@ -4435,6 +4435,7 @@ cache_fplookup_dirfd(struct cache_fpl *fpl,
> struct vnode **vpp)
>         if ((*vpp)->v_type != VDIR) {
>                 if (!((cnp->cn_flags & EMPTYPATH) != 0 &&
> cnp->cn_pnbuf[0] == '\0')) {
>                         cache_fpl_smr_exit(fpl);
> +                       ndp->ni_resflags |= NIRES_EMPTYPATH;
>                         return (cache_fpl_handled_error(fpl, ENOTDIR));
>                 }
>         }
>

on another look it already works fine as is, I miseed the ! in the condition ;)

#include <sys/stat.h>
#include <fcntl.h>

int
main(void)
{
        struct stat sb;
        int fd;

        fd = open("/etc/fstab", O_RDONLY);

        fstatat(fd, "", &sb, AT_EMPTY_PATH);
}

openat(AT_FDCWD,"/etc/fstab",O_RDONLY,00)        = 3 (0x3)
fstatat(3,"",{ mode=-rw-r--r-- ,inode=370100,size=145,blksize=4096
},AT_EMPTY_PATH) = 0 (0x0)

dtrace -n 'vfs:fplookup:: /execname == "a.out"/ { @[stack(), arg1,
arg2] = count(); }'
[snip]
              kernel`kern_statat+0xec
              kernel`sys_fstatat+0x27
              kernel`amd64_syscall+0x109
              kernel`0xffffffff809726bb
             4980                3                1

as in handled in cache_fplookup_emptypath

>
> On 5/2/23, Dmitry Chagin <dchagin@freebsd.org> wrote:
>> On Tue, May 02, 2023 at 03:04:37PM -0400, Mark Johnston wrote:
>>> On Tue, May 02, 2023 at 08:00:01PM +0300, Dmitry Chagin wrote:
>>> > On Tue, May 02, 2023 at 03:12:51PM +0000, Konstantin Belousov wrote:
>>> > > The branch main has been updated by kib:
>>> > >
>>> > > URL:
>>> > > https://cgit.FreeBSD.org/src/commit/?id=a1d71cebc05ccfeedf95f2db3e94b17270167888
>>> > >
>>> > > commit a1d71cebc05ccfeedf95f2db3e94b17270167888
>>> > > Author:     Konstantin Belousov <kib@FreeBSD.org>
>>> > > AuthorDate: 2023-05-02 15:11:39 +0000
>>> > > Commit:     Konstantin Belousov <kib@FreeBSD.org>
>>> > > CommitDate: 2023-05-02 15:11:39 +0000
>>> > >
>>> > >     fstatat(2): restore AT_EMPTY_PATH handling
>>> > >
>>> > >     Fixes:  cb858340dcbf214cc4c4d78dbb741620d7b3a252
>>> > >     Reported by:    markj
>>> > >     Sponsored by:   The FreeBSD Foundation
>>> > > ---
>>> > >  sys/kern/vfs_syscalls.c | 6 +++++-
>>> > >  1 file changed, 5 insertions(+), 1 deletion(-)
>>> > >
>>> > > diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
>>> > > index 5c0a291e3b0b..d68af4ea4d51 100644
>>> > > --- a/sys/kern/vfs_syscalls.c
>>> > > +++ b/sys/kern/vfs_syscalls.c
>>> > > @@ -2438,8 +2438,12 @@ kern_statat(struct thread *td, int flag, int
>>> > > fd, const char *path,
>>> > >  	    AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH) | LOCKSHARED | LOCKLEAF |
>>> > >  	    AUDITVNODE1, pathseg, path, fd, &cap_fstat_rights);
>>> > >
>>> > > -	if ((error = namei(&nd)) != 0)
>>> > > +	if ((error = namei(&nd)) != 0) {
>>> > > +		if (error == ENOTDIR &&
>>> > > +		    (nd.ni_resflags & NIRES_EMPTYPATH) != 0)
>>> > > +			error = kern_fstat(td, fd, sbp);
>>> > >  		return (error);
>>> > > +	}
>>> >
>>> > cache_fplookup_dirfd() doesnt set the NIRES_EMPTYPATH flag
>>>
>>> It doesn't, but for an AT_EMPTY_PATH lookup it aborts the lookup and
>>> returns ENOTDIR to namei(), which sets NIRES_EMPTYPATH before passing
>>> the error up.
>>>
>>
>> it call cache_fpl_handled_error() which is set status to
>> CACHE_FPL_STATUS_HADLED, namei() simply return error in that path
>>
>>
>>> > >  	error = VOP_STAT(nd.ni_vp, sbp, td->td_ucred, NOCRED);
>>> > >  	NDFREE_PNBUF(&nd);
>>> > >  	vput(nd.ni_vp);
>>> >
>>
>
>
> --
> Mateusz Guzik <mjguzik gmail.com>
>


-- 
Mateusz Guzik <mjguzik gmail.com>